With the NXE update it is possible to run games from HDD without the disc. The trick is that it has to read the disc to initialize. The disc is used to start the game and then removed via an opened DVD drive. Note that this is not a new way to pirate games, it requires a legitimate copy of a game. It also won't get you free games from your friends, unless you seriously want to leave your 360 torn apart and call your friend every time you want to play the game. I think it is a good way to play System Link on new games though, I bought the Halo Wars Limited Edition but none of my friends have the game to play multiplayer with. (less info)